We have only an idea of what this thing is, but it is surely unique. One idea is that it is a fid, but it doesn’t really look like one, but it could have been used to open up the "lay" of large rope. Another idea is that it was used for caulking - ie hammering in the caulking on a ship. Someone thought it might have been used for fishing – taking the hook out of large fish. It also could be made by a sailor as a hammer for his child. Anyway, "it is what it is" and I love it. If anyone has an idea please let me know.